In 1963, Haidu signed with Dinamo București, helping the team win The Double in his first season, coaches Nicolae Dumitru and Traian Ionescu using him in 21 games in which he scored six goals, also playing all the minutes in the 5–3 victory over rivalsSteaua București from the Cupa României final.[1][4][5] In the same season he started to play in European competitions, making three appearances in the European Cup, helping his side pass East Germany champion, Motor Jena but being eliminated in the following phase by Real Madrid.[1][6] In the following season, Haidu helped The Red Dogs win another title, contributing with a personal record of 10 goals scored in the 23 matches he was used by coach Angelo Niculescu, including finding the net in a 1–0 win in the derby with Steaua.[1][4][7] In the 1965–66 European Cup edition he scored the victory goal in a 2–1 with Inter Milan, after which he said:"I'm happy for the success, but I'm also sad that we didn't impose ourselves more clearly", eventually the second leg being lost with 2–0.[1][8] He won two more trophies with Dinamo, the 1967–68 Cupa României when coach Bazil Marian used him all the minutes in the 3–1 victory over Rapid București from the final and the 1970–71 title when he scored two goals in the 14 matches played under the guidance of coaches Nicolae Dumitru and Traian Ionescu.[1][4][9]
In 1972, Haidu went to play for Chimia Râmnicu Vâlcea in Divizia B, winning the 1972–73 Cupa României, being used by coach Dumitru Anescu all the minutes in both games from the final with Constructorul Galați.[1][10] In the 1973–74 season he played in both legs of the 4–2 loss on aggregate in front of Glentoran from the European Cup Winners' Cup, having a total of 15 games with one goal scored in European competitions, also at the end of the season the team earned promotion to the first league.[1][11] In the following season, Haidu made his last Divizia A appearance, playing for Chimia on 29 June 1975 in a 3–0 away loss with Politehnica Iași, having a total of 201 matches with 46 goals scored in the competition.[1]
Haidu made four appearances and scored two goals at international level for Romania, scoring the victory goal in his debut game, a 3–2 win over East Germany which took place on 12 May 1963, playing under the guidance of coach Silviu Ploeșteanu.[1][15][16] In his second game for the national team he opened the score in a 1–1 with Poland.[15][17] He also played four games and scored one goal for Romania's Olympic team.[15]
International goals
Scores and results list Romania's goal tally first, score column indicates score after each Haidu goal.[15][16][17]
In July 1973, the Romanian magazine called Fotbal described Haidu's style of play:"Here (at Dinamo București) he will determine, in a way, that "Internazionale tactic" that has brought the Red and Whites the suite of four national titles in good measure. In the economy of that tactic, developed by coach Traian Ionescu, Haidu had one of the mission roles similar to that of Zagallo in the Brazil team or Corso in the aforementioned Milan formation. He would appear as the third man in the midfield (next to Emil Petru and Octavian Popescu) but you could also find him advanced, centering for the "bulldozers" Ene II or Frațilă".[2]
